Further infrared systems studies for the earth resources program Final report

Design of multispectral scanner for orbital earth resources detectio

A Young Globular Cluster in the Galaxy NGC 6946

A globular cluster ~15 My old that contains 5x10^5 Msun of stars inside an 11 pc radius has been found in the nearby spiral galaxy NGC 6946, surrounded by clouds of dust and smaller young clusters inside a giant circular bubble 300 pc in radius. At the edge of the bubble is an arc of regularly-spaced clusters that could have been triggered during the bubble's formation. The region is at the end of a spiral arm, suggesting an origin by the asymmetric collapse of spiral arm gas. The globular is one of the nearest examples of a cluster that is similar to the massive old globulars in the Milky Way. We consider the energetics of the bubble and possible formation mechanisms for the globular cluster, including the coalescence of smaller clusters.Comment: 20 pages, 7 figures, accepted for Astrophysical Journal Vol 535, June 1 200

Stable and Unstable Circular Strings in Inflationary Universes

It was shown by Garriga and Vilenkin that the circular shape of nucleated cosmic strings, of zero loop-energy in de Sitter space, is stable in the sense that the ratio of the mean fluctuation amplitude to the loop radius is constant. This result can be generalized to all expanding strings (of non-zero loop-energy) in de Sitter space. In other curved spacetimes the situation, however, may be different. In this paper we develop a general formalism treating fluctuations around circular strings embedded in arbitrary spatially flat FRW spacetimes. As examples we consider Minkowski space, de Sitter space and power law expanding universes. In the special case of power law inflation we find that in certain cases the fluctuations grow much slower that the radius of the underlying unperturbed circular string. The inflation of the universe thus tends to wash out the fluctuations and to stabilize these strings.Comment: 15 pages Latex, NORDITA 94/14-

Quantum Coherent String States in AdS_3 and SL(2,R) WZWN Model

In this paper we make the connection between semi-classical string quantization and exact conformal field theory quantization of strings in 2+1 Anti de Sitter spacetime. More precisely, considering the WZWN model corresponding to SL(2,R) and its covering group, we construct quantum {\it coherent} string states, which generalize the ordinary coherent states of quantum mechanics, and show that in the classical limit they correspond to oscillating circular strings. After quantization, the spectrum is found to consist of two parts: A continuous spectrum of low mass states (partly tachyonic) fulfilling the standard spin-level condition necessary for unitarity |j|< k/2, and a discrete spectrum of high mass states with asymptotic behaviour m^2\alpha'\propto N^2 (N positive integer). The quantization condition for the high mass states arises from the condition of finite positive norm of the coherent string states, and the result agrees with our previous results obtained using semi-classical quantization. In the k\to\infty limit, all the usual properties of coherent or {\it quasi-classical} states are recovered. It should be stressed that we consider the circular strings only for simplicity and clarity, and that our construction can easily be used for other string configurations too. We also compare our results with those obtained in the recent preprint hep-th/0001053 by Maldacena and Ooguri.Comment: Misprints corrected. Final version to appear in Phys. Rev.

Sulfate Reduction in Sediments Produces High Levels of Chromophoric Dissolved Organic Matter

Sulfate reduction plays an important role in altering dissolved organic matter (DOM) in estuarine and coastal sediments, although its role in the production of optically active chromophoric DOM (CDOM) and a subset of fluorescent DOM (FDOM) has not been previously investigated in detail. Freshwater sediment slurries were incubated anaerobically with added sulfate and acetate to promote sulfate-reducing bacteria. Ultraviolet visible (UV-Vis) absorbance and 3-dimensional excitation emission matrix (EEM) fluorescence spectra were measured over a five weeks anaerobic dark incubation period. Parallel Factor Analysis (PARAFAC) of FDOM determined components that increased significantly during dark and anaerobic incubation matching three components previously considered of terrestrially-derived or humic-like origin published in the OpenFluor database. The observed FDOM increase was strongly correlated (R2 = 0.96) with the reduction of sulfate. These results show a direct experimental link between sulfate reduction and FDOM production, which impacts our understanding of coastal FDOM sources and early sediment diagenesis. As 3D fluorescence techniques are commonly applied to diverse systems, these results provide increasing support that FDOM can have many diverse sources not consistently captured by common classifications such as “humic-like” fluorescence

From the WZWN Model to the Liouville Equation: Exact String Dynamics in Conformally Invariant AdS Background

It has been known for some time that the SL(2,R) WZWN model reduces to Liouville theory. Here we give a direct and physical derivation of this result based on the classical string equations of motion and the proper string size. This allows us to extract precisely the physical effects of the metric and antisymmetric tensor, respectively, on the {\it exact} string dynamics in the SL(2,R) background. The general solution to the proper string size is also found. We show that the antisymmetric tensor (corresponding to conformal invariance) generally gives rise to repulsion, and it precisely cancels the dominant attractive term arising from the metric. Both the sinh-Gordon and the cosh-Gordon sectors of the string dynamics in non-conformally invariant AdS spacetime reduce here to the Liouville equation (with different signs of the potential), while the original Liouville sector reduces to the free wave equation. Only the very large classical string size is affected by the torsion. Medium and small size string behaviours are unchanged. We also find illustrative classes of string solutions in the SL(2,R) background: dynamical closed as well as stationary open spiralling strings, for which the effect of torsion is somewhat like the effect of rotation in the metric. Similarly, the string solutions in the 2+1 BH-AdS background with torsion and angular momentum are fully analyzed.Comment: 24 pages including 4 postscript figures. Enlarged version including a section on string solutions in 2+1 black hole background. To be published in Phys. Rev. D., December 199

Valuation of aircraft noise by time of day: a comparison of two approaches

This paper reports an innovative application of stated preference techniques to derive values of aircraft noise by time of day and day of week. Revealed preference techniques cannot provide such segmentations which would clearly be of use in policy development especially relating to airport operations. Given the lack of research on this issue the work reported here is highly experimental. Two stated preference experiments were designed. The first focussed on a single time period whilst the second asked respondents to trade between time periods. Both approaches yielded results that are plausible and mutually consistent in terms of relative values by time period. We conclude that stated preference techniques are particularly useful in this context where the use of aggregated values may lead to non-optimal policy decisions

The Snapshot Hubble U-Band Cluster Survey (SHUCS) II. Star Cluster Population of NGC 2997

We study the star cluster population of NGC 2997, a giant spiral galaxy located at 9.5 Mpc and targeted by the Snapshot Hubble U-band Cluster Survey (SHUCS). Combining our U-band imaging from SHUCS with archival BVI imaging from HST, we select a high confidence sample of clusters in the circumnuclear ring and disk through a combination of automatic detection procedures and visual inspection. The cluster luminosity functions in all four filters can be approximated by power-laws with indices of $-1.7$ to $-2.3$. Some deviations from pure power-law shape are observed, hinting at the presence of a high-mass truncation in the cluster mass function. However, upon inspection of the cluster mass function, we find it is consistent with a pure power-law of index $-2.2\pm0.2$ despite a slight bend at $\sim$$2.5\times10^{4}$ M$_{\odot}$. No statistically significant truncation is observed. From the cluster age distributions, we find a low rate of disruption ($\zeta\sim-0.1$) in both the disk and circumnuclear ring. Finally, we estimate the cluster formation efficiency ($\Gamma$) over the last 100 Myr in each region, finding $7\pm2$% for the disk, $12\pm4$% for the circumnuclear ring, and $10\pm3$% for the entire UBVI footprint. This study highlights the need for wide-field UBVI coverage of galaxies to study cluster populations in detail, though a small sample of clusters can provide significant insight into the characteristics of the population.Comment: 31 pages, 9 figures, accepted to the A

Improved Deposition and Performance of a Microencapsulated Sex Pheromone Formulation for Codling Moth (Lepidoptera: Tortricidae) with a Low Volume Application

Experiments were conducted to evaluate the deposition pattern and effectiveness in disrupting male orientation to virgin female-baited traps of a microencapsulated sex pheromone formulation for codling moth, Cydia pomonella (L.) in apple, Malus domestica Bordhausen. The efficacy of two application techniques was evaluated in field trials with the microencapsulated formulation Checkmate® CM-F: a high volume (926 liters per ha) application with an air blast sprayer and a low volume (46 liters per ha) application with a custom-built vertical boom sprayer. These treatments were compared to an unsprayed control and a control treatment where the formulation was applied directly on the ground within the plots. Disruption of virgin female-baited traps was significantly greater in the low volume versus the air blast application and versus the two types of control plots. Levels of disruption in the air blast-sprayed plots were not different from untreated plots or in plots where the sprayable sex pheromone was applied directly on the ground. A significant increase in the proportion of traps catching moths occurred in week 4. A significant interaction occurred among the effects of spray method, tree canopy position, and leaf surface on microcapsule deposition. This interaction was likely due to the low rate of deposition of microcapsules on the undersides of leaves in the lower canopy with the low volume sprayer. The low volume sprayer deposited significantly more microcapsules in the upper canopy than the air blast sprayer. Significantly more microcapsules were deposited on the underside versus the top of leaves in the upper canopy with the air blast but not with the low volume sprayer